In several kinds of devices and machines the need sometimes arises to selectively put two environments in communication or to separate one environment from the other, alternatively. For example, one space or environment can be formed by a product container, the product contained therein being selectively dispensed in a second space or environment, in which a device acting upon the product is arranged.
In beverage producing machines, for example, containers for beverage ingredients in the form of bulk material, e.g. in granular or powder form, are provided. The ingredients contained in the containers must be selectively dispensed toward a brewing unit, a mixer or any other kind of apparatus, device, or component in which the beverage or a part thereof is prepared, for example using hot water flowing through a metered amount of beverage ingredient(s).
In some circumstances two mutually adjoining spaces or environments must be separated from one another when no flow of product is required from one environment to the other, but they must be placed into communication if a product should flow from one space in the other.